1. Field of the Invention
The present invention relates to an in-vehicle image display device that displays images captured with in-vehicle cameras.
2. Background Art
Display systems that display an image of the peripheral area of a vehicle to assist drivers in checking the peripheral area of the vehicle have been in widespread use, in which a wide-angle camera is mounted on the vehicle and an image captured with the camera is displayed on a monitor installed on the side of the driver's seat. Typical among monitors installed on the driver's seat are compact monitors with a screen size of about 7 to 10 inches due to the restrictions of the interior room space of the vehicle.
A display system that displays an image of the peripheral area of a vehicle has one or more cameras mounted on the vehicle. When two or more cameras are mounted on the vehicle with such a display system that displays an image of the peripheral area of the vehicle, a monitor installed on the side of the driver's seat is configured to display one of the camera images with a manual switching operation of the driver, display two or more camera images side-by-side, or display a single image formed by combining the two or more camera images.
Reference 1 (JP Patent Publication (Kokai) No. 2007-288611 A) discloses a technique for processing images captured with wide-angle cameras that are installed on the four sides, including the front side, rear side, left side, and right side, of a vehicle with a signal processing device, displaying a top-view image formed through a viewpoint conversion process such that the resulting image appears to be viewed from a virtual viewpoint right above the vehicle, and displaying alongside the top-view image at least one of the images captured with the cameras on the front side, rear side, left side, and right side of the vehicle.
A top-view image is an image formed by combining the camera images of the front side, rear side, left side, and right side of the vehicle based on the ground surface around the vehicle as a reference. Using a top-view image is advantageous in that the driver can recognize at a glance the conditions of the entire peripheral area of the vehicle, while it is also disadvantageous in that stereoscopic objects could be displayed in a distorted manner as a result of the viewpoint conversion and an image of the area above the ground surface could not be not displayed.
According to Reference 1, images captured with the cameras installed on the front side, rear side, left side, and right side of the vehicle are displayed alongside the top-view image to compensate for the aforementioned disadvantages of the top-view image. Specifically, Reference 1 discloses a technique of selecting a camera image to be displayed alongside the top-view image in accordance with the vehicle speed or the vehicle travelling direction. For example, when the vehicle drives in reverse to the right, the cameras on the right side and rear side of the vehicle are selected.
With regard to a display system that displays an image of the peripheral area of a vehicle using a top-view image, Reference 2 discloses a method using an obstacle sensor installed on the vehicle, which includes enlarging and displaying, upon detection of an obstacle around the vehicle with the obstacle sensor, the peripheral area of the detected obstacle around the vehicle on the top-view image.